The present invention is directed generally to electrical switches, and more particularly to a miniature, two-level, low profile pushbutton switch for making at least one circuit at each of two levels of actuation thereof.
Such two-level switches are generally known. In many applications it is desirable to have a relatively low-travel switch which is nonetheless capable of making different circuits at different levels of travel thereof. Such switches are useful, for example, in conjunction with a camera having a self-contained metering system. In such applications, the first level of contact of such a switch is often utilized to actuate the metering system of the camera, and the second level thereof utilized to actuate the shutter of the camera for exposing a frame of film. In this application, the user may desire to check for proper exposure and hence actuate only the metering system without actually exposing a frame of film. Hence, depression of the switch only to its first level in order to observe a metering indicator may be desirable in many cases. Moreover, in many cameras the self-contained metering system also controls exposure time and hence shutter actuation. Accordingly, the metering system must remain energized during energization of the shutter. While such two-level pushbutton switches are not new, as such, there remains room for improvement. For example, many such switches heretofore in use, due to their relatively small size, have provided minimal internal contact surfaces for making the two circuits required, as described above. With such minimal contact surfaces, there is an increased danger of loss of electrical switching function due to wear or deformation of the parts over a period of service. While contact wear may cause an open circuit, excessive deformation of parts may cause a permanent short circuit in the switch. Both of the foregoing short circuit conditions prevent proper functioning of the switch and associated circuits.
Moreover, such switches must generally be provided in relatively large quantities at a competitive price, in order to be used on relatively inexpensive equipment, such as low-cost cameras. Accordingly, it is important to minimize the number of components utilized and yet maximize the ease with which these components may be assembled into a reliable low-cost switch.